code: def before_validate(self):
      # put model in training mode so we can calculate losses for validation
      self.model.train()
  
file_path: icevision/icevision/models/torchvision/fastai_callbacks.py
imports: from icevision.imports import *
  from icevision.engines.fastai import *
label_desc: Use image node_id 4 for calling the RCNNCallback obj's underlying member method code with example usage: obj.before_validate() without return types